Multi-view projection microscope



= i s RFERENGE swan R00 350-169 v March 15, 1966 ERBAN 3,240,112

MULTI-VIEW PROJECTION MICROSCOPE Filed Dec. 12, 1960 2 Sheets-Sheet 1 HVVENTOR.

March 15, 1966 R. T- ERBAN 3,240,112

MULTI-VIEW PROJECTION MICROSCOPE Filed Dec. 12, 1960 2 Sheets-Sheet 2 IN V EN TOR.

Patented Mar. 15, 1966 3,240,112 MULTI-VIEW PROJECTION MICROSCOPE Richard T. Erhan, 14538 Bayside Ave., Flushing 54, NCY. Filed Dec. 12, 1960, Ser. No. 75,329 Claims. (Cl. 8824) This invention relates to projection microscopes in which the light reflected from the observed object is utilized to produce an enlarged real image of the object.

Instruments of this kind are useful for inspection of small parts and met-a1 cutting tools where the conditions of the cutting edge are of prime importance for the quality of the work produced. Such tools must be inspected to avoid their use when the cutting edges are dulled beyond a certain degree in order to avoid destructive damage to the work piece and the tool itself.

Optical comparators have been used to produce on their screen an enlarged view of such tools in order to permit the operator to determine the amount of wear or damage on the cutting edges and specify the amount of material to be removed by the tool grinder.

In many cases it is difficult to get a clear understanding of the nature and extent of the wear or damage by viewing an image on a flat screen because the tool and its details are three dimensional in space While the image on the screen is only a fiat picture.

It is among the objects of the present invention to provide an instrument that will transmit a clear understanding of the spacial structure of an observed object by projecting closely adjacent to each other several images upon the same screen, with each image representing a view of the object taken from a different direction than the others. By a visual integration of these several views the observer gains an immediate and clear perception of curved surfaces and even of intricate configurations of the object.

These and other objects of the invention, which will from time to time be pointed out in the following specification are illustrated by way of example in the accompanying drawings wherein:

FIGURE 1 is a sectional elevation of the instrument.

FIGURE 2 is a schematical section of a detail of FIGURE 1.

FIGURE 3 is a view in a 2:1 scale of the central portion of the instrument of FIGURE 1 as seen from below as indicated by the arrows AA.

FIGURE 4 is a partial section of an elevated view similar to FIGURE 1 illustrating additional details at a 2:1 scale with respect to FIGURE 1.

FIGURE 5 is a front view of a complete instrument.

FIGURE 6 is a partial view of a special cutting tool similar to the one illustrated in FIGURES 1, 3, and 4.

Referring now to FIGURE 1 there is shown a cabinet 2 having a horizontal top plate 4 provided with an aperture 5. Above the top plate 4 is fastened a support 7 which has a central pivot 8 upon which a disc shaped rotary cutter 10 is freely rotatable. The rim 11 of the cutter is provided with protruding teeth 12. This may be seen more clearly from FIGURE 6 where a portion of the cutter 10 is shown with the rim 11 and the cutter teeth 12 in schematical perspective. Similar cutters are used in machine tools for the manufacture of bevel gears such as the well-known Gleason generator. It is noted, however, that the teeth as illustrated in FIGURE 6 are not a true picture of a Gleason cutter and indicate only the general position and form.

It is noted that the shape of the teeth in FIGURE 6 is only schematical, while the shapes shown in FIGURE 5 are scaled down versions of a tracing made on the screen of an actual instrument embodying the invention.

In order to convey to the observer a complete and clear understanding of the tooth shape and the extent of the wear or damage on it, the instrument shows on its screen closely adjacent to each other three different views of each tooth. The composite image as it appears upon the screen is illustrated in FIGURE 5, At the left side of the screen 50 appears a side view C of the tooth, which is the enlarged image taken in the direction of the arrows C in FIGURE 6. At the right side of the screen 34 appears a. side View D which is the enlarged image taken in the direction of the arrow D is FIGURE 6. In the middle of the screen 51 between the images C and D appears the image B of the tooth as seen in the direction of the arrow B in FIGURE 6.

It is noted that the shape of the teeth in FIGURE 6 is only schematical, while the shapes shown in FIGURE 5 are scaled-down versions of an actual tracing made from a Gleason cutter on the screen of an instrument built in accordance with this disclosure of the invention.

It is seen that the cutter 12 (FIGURE 5) has its center to the left of the middle of the instrument, similar to its positions shown in FIGURES 1, 3, and 4. Since the image of the cutter is produced by the projection objective 14, FIGURE 1, the projected image has right and left sides reversed, and the screen image B of the cutter has its center on the right side, that is, the contour of the cutter is a circle curved to the right side.

The projection microscope shown in FIGURE 5 positioned on top of the screen 50 is to be understood to be the same as the one illustrated in detail in FIGURES 1 and 4; the projection beam 17 emanating from the optical objective 14 is understood to be directed unto the screen 50 by suitably positioned mirrors; since this detail is a conventional structure and does not form part of this invention, it is not illustrated in FIGURE 5.

The magnifications used may vary from about 5 to over 50 diameters, depending on the object; in the case illustrated, the height of the teeth of the Gleason cutter was .250 inch, and the height of the projected image (C in FIGURE 5) was from 2.5 inches for a screen 16 inches wide to 7.5 inches for a 48-inch wide screen.

Referring again to FIGURE 1, it is seen that the objective 14 is mounted with its optical axis 32 in a vertical position below the stage opening at 5 so that the central portion of an object put upon the stage will find itself substantially upon the optical axis of the projection objective. In other words, the projection objective is focused upon the center of the stage; the aperture of the objective and its focal length are so chosen that the total field (object field) covered by it has a diameter of at least 2.5 to 5 times the mean diameter of the central stage. The objective 14 will then project upon the screen the image of the object on the stage center surrounded by background of the stage.

Now when small mirrors 6-6 (FIGURE 1) are placed adjacent to the object 1I12, and inclined towards the object 14 at the proper angle, the objective 14 will pick up two side views of the cutter tooth 12, one view from the inside and one view from the outside.

The view of the stage with the cutter placed upon it and the two mirrors 66 in correct position is illustrated in FIGURE 3 which shows what an observer would see if he were looking from the place of the objective 14 (FIGURE 1) in the direction of the arrows A--A.

There is seen in FIGURE 3 in dotted lines the cutter 10 with rim 11, and in full lines that part which is visible through the stage opening 5. Also visible are the two small mirrors 66; each of said mirrors presents a side view of the tooth 12 which is between them. The

mirror on the left side shows the inside image of the cutter tooth while the mirror on the right side shows the side view C of the tooth from the outside, corresponding to the direction C of FIGURE 6. In the middle between the image C and D appears the tooth B as seen directly, similar to the view B in FIGURE 6.

The images projected by the objective 14, are produced only by light which is reflected or scattered from the surface of the object 12. With the exception of well polished surfaces, such reflection will be non-specular, that is, the reflected light is scattered or diffused. The amount of light collected by the objective 14 depends on its numerical aperture, the magnification ratio of the projection and the intensity of illumination of the object as reduced by the coeflicient of reflection of the object surface. A very high intensity of illumination is required if the projected screen image is to be visible in normally lighted rooms of about ft. cdle.

The angle of incidence of the illuminating light beam is also an important factor. Illumination which is perpendicular to the observed surface tends to give flat pictures of little contrast that reveal not much detail, and in case of a portion of the surface being specularly reflective, the glare caused by the specular reflection will cover up all surrounding detail, much as the headlights of an oncoming car obliterate the immediate neighborhood. It is therefore necessary to provide a slanting illumination of a mean angle of substantially not less than relative to the axis of the cone of reflected light which is collected by the projection objective.

It is also necessary to provide means by which the angle of incidence of the illuminating light can be changed to suit the object. This is more fully explained in FIG- URE 3.

In FIGURE 1, the illumination is provided by two substantially similar condenser systems. Each system consists of a projection lamp 21, a reflector 20, a first condenser lens 22, a second condenser lens 24 and a heat filter 23 interposed between the two condenser lenses. All of these elements are centered upon an optical axis 29. This system produces a slightly convergent beam as indicated in dotted lines in FIGURE 1 for the condenser system at the left side up to the point where this beam enters the prism 25. The optical axis 29 of each system is inclined at substantially not over against the horizontal top plate 4, because conventional projection lamps 21-21 will not stand prolonged operation if inclined at angles greater than 25 to the vertical.

In order to give the illuminating beam in each system the desired direction with respect to the rays of the viewing beam between the object and the objective, the prisms 25 are made tiltable about an axis indicated by the pivots 3131 in FIGURES 3 and 4. The prisms are held in brackets 30 (FIGURES 3, 4) which are fastened to the top plate 4. It is understood that both prisms are so mounted, although it is shown for one prism only. Similarly this adjustable mounting has not been shown in FIGURE 1 to avoid crowding the drawing.

The illuminating beam with the central ray 29 is deflected from about 25 inclination to the horizontal to substantially between 45 and 65 by the prism of suitable angle and set to the optimal position. In most cases of small objects to be projected at magnifications of over 10 diameters, the very high intensity of illumination required to give a legible image on the screen is obtained by a third condenser lens 26 which is combined with the prism 25. The optical axis 41 of the lenses 26 is offset laterally from the point of exit of the central ray 49 from the prism in order to increase the deflection angle. The central ray which exits from the last condenser lens 26 has the direction 59 as seen in FIGURE 4. It is understood that the second condenser system is arranged in the same manner.

FIGURE 4 illustrates the path of the illuminating rays through the final elements of the condenser system 25-26 to the object 12. The upper ray 37-47-57 impinges upon the cutter near the root of the tooth on the inner side face D; the central ray impinges near the tip of the tooth; while the lower ray 37-47 by-passes the object and impinges upon the right side plano reflector (mirror) 6 where it is reflected as ray 57 towards the outer side face C. It follows therefrom that one portion of the illuminating beam reaches the object directly while another portion reaches it after reflection by the plano reflectors which serve to transmit the side views to the projection objective whereby they serve a double function as image collectors and as illumination transmitting means.

FIGURE 4 discloses a detail structure which is shown also in FIGURE 1, concerning the plano reflectors 6-6. They are mounted on brackets 3838 which in turn are adjustable by the rack and pinion drive 39-40 respectively. This is done in order to adjust the mirrors 6-6 to equalize the optical distances between the object 12 and the objective 14. The viewing beams between the objective 14 and the object 12 are denoted by their boundary rays, which are 1616 for the Viewing beam that transmits the direct view of the tooth 12 to the objective 14. The left side image is transmitted by the beam within the boundary rays 4242 which are reflected by the left side mirror 6, coming from the face D" of the tooth 12. Similarly, the right side image emanating from the outside face C between the rays 44 and 45 and reflected by the right side mirror 6 in a direction generally parallel to the optical axis 32, reaches the objective 14 between the rays 4343. So far, the presence of the lenses 27 27 and 28 in the path of these beams has been disregarded. It is seen that without these lenses, the optical distances from the projection objective 14 to the top of the object 12 and to its sides via the mirrors 6 respectively are unequal, the optical distances for the beams 4242 and 43-43 being substantially longer than the distance for the direct viewing beam 16-46. If left without compensation, this would result in having to re-focus the objective 14 by means of the knob 15 every time the observation changes from the side views C'-D' to the center view B.

Simultaneous sharply focused images (also called parfocal images) are obtained by inserting some or all of the lenses 2727, 28 in the manner shown in FIGURE 4. Considering first the use of the positive lenses 2727 only, it is seen that they constitute two halves of a single lens which has a strip through the middle of it cut out. This is also illustrated in FIGURE 1 where it is seen that this cut out is of such width that the beam necessary for transmitting the central or direct view image can pass through. The viewing beams for the side images as illustrated in FIGURE 4 pass the split lens parts 2727 and a similar ray tracing is applicable to FIGURE 1, but has been omitted for the sake of clarity of the drawing. From an inspection of FIGURE 4 it is clear that each split lens is inserted in one of the two beams and is effective to reduce the equivalent focal distance to the value of the central beam, so that all three images are par-focal and appear in sharp outlines simultaneously on the screen.

Instead of using positive lenses to reduce the equivalent length of the side viewing beams, a single negative lens may be inserted in the beam of the central image with the result of lengthening the equivalent focal distance for this beam to the same value as the side beamsv Finally, both methods may be combined, in which case lenses of less power can be employed. A further improvement is illustrated in FIGURES 2 and 3 where each of the split half lenses 2727 is connected by a bracket 34 to a rack 35 which can be adjusted through a pinion 36 and a control knob 33. In FIGURE 3 only one such control mechanism is shown to avoid crowding the drawing; while in FIGURES 1 and 4 this mechanism has been omitted, it is to be understood that it may be equally incorporated. In another alternative to the structure shown in FIG. 2, the two halves 2727 are made in one part, that is, the original lens 27 is not split, but a plano-parallel strip is ground through the middle part of it, Wide enough to let the beam for the central view pass through. This variant is not illustrated because it appears clearly understandable by description. It must be remarked however that in this case where the two halves 2727 form one solid piece, the individual adjustment illustrated in FIG. 2 cannot be used. Slight differences in the focal length of the two side-view beams must then be equalized by adjustment of the position of the mirrors 6, individually through the rack and pinion drive 3940 shown in FIG. 4. A still further variant of this structure is obtained by grinding into the center of a positive lens which replaces the two halves 2727, a small negative portion which is wide enough to let the central view beam pass through. This could be compared to a bi-focal lens of an eye glass as to its general structure, the difference being in the location of the individual elements, their centers of curvature and their focal equivalent length which must be adapted to the special focal length and projection distance of the objective 14.

Another aspect of this invention shall be described. on hand of FIG. 4. While it has heretofore been pointed out that the two illuminating systems and their optical elements are substantially the same, and therefore the illumination obtained on the object might be expected to be substantially equal to that obtained by a single sys tem, it is seen from an inspection of FIG. 4 that the illuminating rays from the two systems respectively have different angles of incidence upon the same portion of the object, even when the central rays of the two systems, 29 and 29' respectively, have the same basic angle with respect to the top plate 4, as shown in FIG. 4. It is seen that the outside of the tooth 12 near its tip is illuminated from the right side by rays very close to the central ray 29', and that at the same time it receives light from the left condenser system by rays near the bottom ray 3747'57' after its reflection from the mirror 6 at the right side of the stage. These differences of the angles of incidence can be further increased by suitable changes in the angular position of either or both of the prisms 25, 25 about the pivots 3131. It has been observed that minute surface details became much more clearly visible when positioned in those zones of the stage Where the angles of incidence for rays from the two beams were markedly different. In contrast hereto, surface details must be much more pronounced, that is of greater dimensions, in order to be perceived under illumination of substantially equal and uniform angles of incidence of the illuminating rays.

It is also to be understood that the two mirrors 66 in FIGS. 1, 3 and 4 may be replaced by other types of optical plano-reflectors, such as a reflecting prism without basically changing the general arrangement of the in strument. Likewise, it will be understood that the general arrangement will remain basically unchanged if the entire instrument is turned upside down, that is, if the stage is positioned at the bottom with the object to be viewed facing upwards, with the projection objective placed above the object and the two illuminating systems sending their beams downwards under substantially the same angle relative to the plate 4 as shown in FIG. 4.

It will be understood that the disclosures herein of the various embodiments of my invention are by way of illustration only and that they are not to be construed in any limiting sense, and that my invention is not to be considered as limited in any other way then as defined in the appended claims.

Having thus described my invention and illustrated its use, what I claim is:

1. In a multi-view projection microscope for inspection of a rotary cutting tool having a plurality of cutting teeth positioned along its periphery, a stage for holding said cutter freely rotatable, said stage comprising a substantially plane support member having a central opening and a shaft positioned to one side thereof, said shaft being adapted to rotatably support said cutter so that rotation of said cutter causes said teeth to move along .a path substantially through the center of said stage with the opposite sides of the surfaces of said teeth being substantially at right angles to the plane of said stage whereby the tangent to the path of the teeth at the center of the stage is parallel to said plane of the stage, an optical objective focused upon the center of said stage and having its optical axis substantially at right angles to said plane of the stage, a plurality of optical condenser systems constructed to direct illuminating light beams towards the center of said. stage, and optical plano reflectors posi- .tioned within the object field of said optical objectives on both sides of and adjacent to the path followed by said teeth of the cutter across the center of said stage so that the teeth can be viewed directly and also the sides of each of the said. teeth can be observed while moving across the stage and while being subject to the changing angles of incidence produced by the interaction of the stationary illuminating beams and the moving cutter teeth and means operable to move said reflectors laterally of the center of said stage.

2. A multi-view projection microscope according to claim 1, including an auxiliary split lens with positive optical power positioned immediately adjacent said. plano reflectors and having the optical axis of said split lens substantially coincident with the optical axis of said optical objective so that the light transmitted from said plano reflectors to said optical objective must pass through said split lens, the spacing between the split parts of the lens being of a width sufficient to permit a direct viewing beam of reflected. light to pass from said object to said optical objective between the parts of said split lens without being affected by said parts.

3. A multi-view projection microscope according to claim 2, comprising individual mounting means for each part of said split lens adapted to provide for each of said lens parts a limited motion of adjustment in a direction parallel to the optical axis of said optical objective.

4. In a multi-view projection microscope of the kind referred to, in combination, a stage positioning the object, means illuminating said object by directing at least two individual beams of light onto said object so that they illuminate substantially opposite sides of said object, a single optical projection objective positioned so that its optical axis when extendedv passes substantially through said object, optical reflecting means positioned laterally of the illuminated opposite sides of the object and so closely spaced therefrom that they lie within the respective beams of light reflected by said opposite sides of the object and simultaneously at least partially within the said beams of illuminating light directed to opposite sides of said object, said optical reflecting means being so inclined with respect to said optical axis and to said opposite sides of the object that they serve the dual function of directing reflected light from the sides of the object towards said optical objective and of directing a portion of the illuminating light beams towards the opposite sides of said object.

5. In a multi-view projection microscope for viewing an object by reflected light emanating from surface portions of said object in directions substantially opposite with respect to each other, a stage having a center part and means for holding the object substantially at said center, an optical projection system including a screen and an optical objective positioned with its optical axis passing through said center of the stage and substantially at right angles to the plane of said stage, means for focusing said objective upon the central portion of said object, plano-reflecting means positioned on opposite sides of the center of said stage closely adjacent said object and inclined at an angle of substantially 45 with respect to said plane of the stage and facing said objective to deflect towards said objective the light rays emanating by reflection from surface portions extending laterally of said central portion of said object, means for limited adjustment of said, lano-reflecting means parallel to said plane of the stage, a lens of negative optical power interposed in the central projection beam of reflected light between said central portion of said object and said optical objective, said negative power lens being positioned in the limited zone of said central projection beam which is closely adjacent said object and which is free from admixture of rays from the projection beams of reflected light which are deflected by said plane-reflectors towards said optical objective.

References Cited by the Examiner UNITED STATES PATENTS Wynne Wilson Wolff Fultz et al.

Mottu Pettavel FOREIGN PATENTS France. 

1. IN A MULTI-VIEW PROJECTION MICROSCOPE FOR INSPECTION OF A ROTARY CUTTING TOOL HAVING A PLURALITY OF CUTTING TEETH POSITIONED ALONG ITS PERIPHERY, A STAGE FOR HOLDING SAID CUTTER FREELY ROTATABLE, SAID STAGE COMPRISING A SUBSTANTIALLY PLANE SUPPORT MEMBER HAVING A CENTRAL OPENING AND A SHAFT POSITIONED TO ONE SIDE THEREOF, SAID SHAFT BEING ADAPTED TO ROTATABLY SUPPORT SAID CUTTER SO THAT ROTATION OF SAID CUTTER CAUSES SAID TEETH TO MOVE ALONG A PATH SUBSTANTIALLY THROUGH THE CENTER OF SAID STAGE WITH THE OPPOSITE SIDES OF THE SURFACES OF SAID TEETH BEING SUBSTANTIALLY AT RIGHT ANGLES TO THE PLANE OF SAID STAGE WHEREBY THE TANGENT TO THE PATH OF THE TEETH AT THE CENTER OF THE STAGE IS PARALLEL TO SAID PLANE OF THE STAGE, AN OPTICAL OBJECTIVE FOCUSED UPON THE CENTER OF SAID STAGE AND HAVING ITS OPTICAL AXIS SUBSTANTIALLY AT RIGHT ANGLES TO SAID PLANE OF THE STAGE, A PLURALITY OF OPTICAL CONDENSER SYSTEM CONSTRUCTED TO DIRECT ILLUMINATING LIGHT BEAMS TOWARDS THE CENTER OF SAID STAGE, AND OPTICAL PLANO REFLECTORS POSITIONED WITHIN THE OBJECT FIELD OF SAID OPTICAL OBJECTIVES ON BOTH SIDES OF AND ADJACENT TO THE PATH FOLLOWED BY SAID TEETH OF THE CUTTER ACROSS THE CENTER OF SAID STAGE SO THAT THE TEETH CAN BE VIEWED DIRECTLY AND ALSO THE SIDES OF EACH OF THE SAID TEETH CAN BE OBSERVED WHILE MOVING ACROSS THE STAGE AND WHILE BEING SUBJECT TO THE CHANGING ANGLES OF INCIDENCE PRODUCED BY THE INTERACTION OF THE STATIONARY ILLUMINATING BEAMS AND THE MOVING CUTTER TEETH AND MEANS OPERABLE TO MOVE SAID REFLECTORS LATERALLY OF THE CENTER OF SAID STAGE. 